1. Field of the Invention
The present invention relates to a photometric device for a camera. A photometric device measures the characteristics of light, including brightness and intensity. The photometric device according to the instant invention eliminates measurement errors, obtains an accurate exposure value for a camera and shortens the time needed for the actual measurement.
2. Description of Related Art
Conventionally, a camera's photometric device divides the subject field into multiple regions and carries out the measurement of the light and determines its brightness and intensity. The device then calculates an exposure value for the camera according to the intensity and brightness. In recent years, this dividing method has become common in photometric devices for cameras. Further, the number of divisions in the process has increased. By increasing the number of divisions, photographic scenes can be appropriately classified and highly detailed control can be carried out according to the particular scene. Thus, in classifying a photographic scene, the greater the number of divisions, the better the quality of photograph.
However, there are situations where different exposure values are required, even when the photographic scenes are divided in similar patterns. For example, when a scene is recognized as having a high ultimate brightness with a large difference in the scene's brightness, the scene may be considered a hypothetical scene of a backlighted person, with the sun in the background. The exposure is calculated for a low-brightness subject. However, if the person is bathed in light that is filtered through trees, even though the scene is similar, the parts illuminated by the sun become over-exposed. Thus, there are scenes that cannot be adequately classified using conventional methods.
Applicant has proposed a photometric device of a camera in Japanese Unexamined patent Application 5-163919, published Dec. 22, 1994, which determines the light brightness pattern of the subject field. This device carries out a frequency analysis of the subject field's light brightness patterns and calculates a corrected exposure value. The corrected exposure values are calculated by weighting certain values for each brightness pattern, based on the brightness determination. Using this method, detailed photometry is possible.
In the above device, in order to eliminate photometric errors and to obtain accurate exposure values, the number of light brightness patterns used in the weighting can be increased. However, if there are too many light brightness patterns, the required calculation time becomes excessive and it is impractical to accurately take photographs.